-r reverses both input and output

backward unpacker + example extended

Cargo.lock

@@ -62,12 +62,6 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
-[[package]]
-name = "lexopt"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "478ee9e62aaeaf5b140bd4138753d1f109765488581444218d3ddda43234f3e8"
-
 [[package]]
 name = "libc"
 version = "0.2.108"
@@ -95,6 +89,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "pico-args"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "db8bcd96cb740d03149cbad5518db9fd87126a10ab519c011893b1754134c468"
+
 [[package]]
 name = "sacabase"
 version = "2.0.0"
@@ -117,12 +117,12 @@ dependencies = [
 
 [[package]]
 name = "upkr"
-version = "0.2.0-pre1"
+version = "0.1.0"
 dependencies = [
  "anyhow",
  "cdivsufsort",
- "lexopt",
  "pbr",
+ "pico-args",
 ]
 
 [[package]]

Cargo.toml

@@ -1,12 +1,12 @@
 [package]
 name = "upkr"
-version = "0.2.0-pre1"
+version = "0.1.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
 cdivsufsort = "2"
-lexopt = "0.2.1"
+pico-args = "0.4"
 anyhow = "1"
 pbr = "1"

asm_unpackers/.gitignore

@@ -1 +0,0 @@
-/build/

asm_unpackers/Makefile

@@ -1,51 +0,0 @@
-build/unpack_riscv64: ../c_unpacker/main.c unpack_riscv.S
-	mkdir -p build
-	riscv64-linux-gnu-gcc -g -static -o $@ $^
-
-test_riscv64: build/unpack_riscv64
-	qemu-riscv64 $< test_data.upk /tmp/out.bin
-	cmp test_data.bin /tmp/out.bin
-
-build/unpack_riscv64.o: unpack_riscv.S
-	mkdir -p build
-	riscv64-linux-gnu-gcc -c -o $@ $?
-
-build/unpack_riscv64.bin: build/unpack_riscv64.o
-	riscv64-linux-gnu-objcopy -O binary --only-section=.text $? $@
-
-disas-riscv64: build/unpack_riscv64.o
-	riscv64-linux-gnu-objdump -d $?
-
-build/unpack_riscv32.o: unpack_riscv.S
-	mkdir -p build
-	riscv64-linux-gnu-gcc -march=rv32imc -mabi=ilp32 -c -o $@ $?
-	
-build/unpack_riscv32.bin: build/unpack_riscv32.o
-	riscv64-linux-gnu-objcopy -O binary --only-section=.text $? $@
-
-disas-riscv32: build/unpack_riscv32.o
-	riscv64-linux-gnu-objdump -d $?
-
-build/unpack_armv6m: ../c_unpacker/main.c unpack_armv6m.S
-	mkdir -p build
-	arm-linux-gnueabihf-gcc -g -static -o $@ $^
-
-test_armv6m: build/unpack_armv6m
-	qemu-arm $< test_data.upk /tmp/out.bin
-	cmp test_data.bin /tmp/out.bin
-
-build/unpack_armv6m.bin: unpack_armv6m.S
-	mkdir -p build
-	arm-none-eabi-gcc -march=armv6-m -c -o build/unpack_armv6m.o $?
-	arm-none-eabi-objcopy -O binary --only-section=.text build/unpack_armv6m.o $@
-	
-build/unpack_c: ../c_unpacker/main.c ../c_unpacker/unpack.c
-	mkdir -p build
-	gcc -g -o $@ $^
-
-test_c: build/unpack_c
-	$< test_data.upk /tmp/out.bin
-	cmp test_data.bin /tmp/out.bin
-
-sizes: build/unpack_armv6m.bin build/unpack_riscv64.bin build/unpack_riscv32.bin
-	ls -l build/*.bin

asm_unpackers/test_data.bin

@@ -1,99 +0,0 @@
-typedef unsigned char u8;
-typedef unsigned short u16;
-typedef unsigned long u32;
-
-u8* upkr_data_ptr;
-u8 upkr_probs[1 + 255 + 1 + 2*32 + 2*32]; 
-#ifdef UPKR_BITSTREAM
-u16 upkr_state;
-u8 upkr_current_byte;
-int upkr_bits_left;
-#else
-u32 upkr_state;
-#endif
-
-int upkr_decode_bit(int context_index) {
-#ifdef UPKR_BITSTREAM
-    while(upkr_state < 32768) {
-        if(upkr_bits_left == 0) {
-            upkr_current_byte = *upkr_data_ptr++;
-            upkr_bits_left = 8;
-        }
-        upkr_state = (upkr_state << 1) + (upkr_current_byte & 1);
-        upkr_current_byte >>= 1;
-        --upkr_bits_left;
-    }
-#else
-    while(upkr_state < 4096) {
-        upkr_state = (upkr_state << 8) | *upkr_data_ptr++;
-    }
-#endif
-   
-    int prob = upkr_probs[context_index];
-    int bit = (upkr_state & 255) < prob ? 1 : 0;
-    
-    int tmp = prob;
-    if(!bit) {
-        tmp = 256 - tmp;
-    }
-    upkr_state = tmp * (upkr_state >> 8) + (upkr_state & 255);
-    tmp += (256 - tmp + 8) >> 4;
-    if(!bit) {
-        upkr_state -= prob;
-        tmp = 256 - tmp;
-    }
-    upkr_probs[context_index] = tmp;
-
-    return bit;
-}
-
-int upkr_decode_length(int context_index) {
-    int length = 0;
-    int bit_pos = 0;
-    while(upkr_decode_bit(context_index)) {
-        length |= upkr_decode_bit(context_index + 1) << bit_pos++;
-        context_index += 2;
-    }
-    return length | (1 << bit_pos);
-}
-
-void* upkr_unpack(void* destination, void* compressed_data) {
-    upkr_data_ptr = (u8*)compressed_data;
-    upkr_state = 0;
-#ifdef UPKR_BITSTREAM
-    upkr_bits_left = 0;
-#endif
-    for(int i = 0; i < sizeof(upkr_probs); ++i)
-        upkr_probs[i] = 128;
-    
-    u8* write_ptr = (u8*)destination;
-    
-    int prev_was_match = 0;
-    int offset = 0;
-    for(;;) {
-        if(upkr_decode_bit(0)) {
-            if(prev_was_match || upkr_decode_bit(256)) {
-                offset = upkr_decode_length(257) - 1;
-                if(offset == 0) {
-                    break;
-                }
-            }
-            int length = upkr_decode_length(257 + 64);
-            while(length--) {
-                *write_ptr = write_ptr[-offset];
-                ++write_ptr;
-            }
-            prev_was_match = 1;
-        } else {
-            int byte = 1;
-            while(byte < 256) {
-                int bit = upkr_decode_bit(byte);
-                byte = (byte << 1) + bit;
-            }
-            *write_ptr++ = byte;
-            prev_was_match = 0;
-        }
-    }
-    
-    return write_ptr;
-}

asm_unpackers/unpack_armv6m.S

@@ -1,162 +0,0 @@
-// armv6-m upkr unpacker by yrlf
-// some optimizations by exoticorn
-
-.syntax unified
-.thumb
-
-.section .text
-
-#define ALIGNUP(n, align) (((n) + (align) - 1) & ~((align) - 1))
-#define PROB_LEN (1 + 255 + 1 + 2*32 + 2*32)
-#define FRAME_SIZE ALIGNUP(PROB_LEN, 4)
-
-// auto upkr_unpack(uint8_t * out, uint8_t * in) -> tuple<uint8_t *, uint8_t *>
-.global upkr_unpack
-.type upkr_unpack, %function
-// r0 .. out_ptr (returned)
-// r1 .. in_ptr (returned)
-// r2 .. state
-// r3 .. offset
-// r4 .. prev_was_literal / decode_length ret
-// r5 .. subroutine arg (preserved)
-// r6 .. decode_bit ret
-// r7 .. probs ptr
-upkr_unpack:
-    push { r4, r5, r6, r7, lr }
-    sub sp, sp, #FRAME_SIZE
-
-    mov r7, sp
-    movs r2, #255
-    adds r2, r2, #(PROB_LEN - 255)
-    movs r3, #128
-.Lclear:
-    subs r2, r2, #1
-    strb r3, [r7, r2]
-    bne .Lclear
-
-.Lloop:
-    movs r5, #0
-    bl upkr_decode_bit
-    beq .Ldata
-.Lmatch:
-    // r6 = 1
-    lsls r5, r6, #8
-    cmp r4, #0
-    beq 1f
-
-    bl upkr_decode_bit
-    beq 2f
-
-1:
-    bl upkr_decode_length
-    adds r3, r4, #1
-    beq .Lend
-2:
-
-    adds r5, r5, #64
-    bl upkr_decode_length
-.Lcopy_loop:
-    ldrb r5, [r0, r3]
-.Lstore:
-    strb r5, [r0]
-    adds r0, r0, #1
-    adds r4, r4, #1
-    blt .Lcopy_loop
-    b .Lloop
-
-.Ldata:
-    movs r5, #1
-
-.Ldata_loop:
-    bl upkr_decode_bit
-    adcs r5, r5, r5
-    lsrs r4, r5, #8
-    beq .Ldata_loop
-    b .Lstore
-
-.Lend:
-    add sp, sp, #FRAME_SIZE
-    pop { r4, r5, r6, r7, pc }
-
-.type upkr_decode_length, %function
-// r0 .. -length tmp (saved)
-// r1 ..
-// r2 ..
-// r3 ..
-// r4 .. -length (returned)
-// r5 .. context index (saved)
-// r6 .. (saved)
-// r7 ..
-upkr_decode_length:
-    push { r0, r5, r6, lr }
-
-    movs r0, #0
-    subs r4, r0, #1
-.Lbit_loop:
-    adds r5, r5, #1
-    bl upkr_decode_bit
-    beq 1f
-
-    adds r5, r5, #1
-    bl upkr_decode_bit
-    beq 2f
-    adds r0, r0, r4
-2:
-    lsls r4, r4, #1
-    b .Lbit_loop
-1:
-    adds r4, r4, r0
-
-    pop { r0, r5, r6, pc }
-
-.type upkr_decode_bit, %function
-// r0 .. tmp / prob (saved)
-// r1 .. in_ptr (modified)
-// r2 .. state (modified)
-// r3 .. scratch (saved)
-// r4 ..
-// r5 .. context index (preserved)
-// r6 .. bit (returned)
-// r7 .. probs ptr (preserved)
-upkr_fill_state:
-    lsls r2, r2, #8
-    ldrb r6, [r1]
-    adds r1, r1, #1
-    orrs r2, r2, r6
-
-upkr_decode_bit:
-    lsrs r6, r2, #12
-    beq upkr_fill_state
-
-    push { r0, r1, r3, lr }
-
-    ldrb r0, [r7, r5]
-
-    lsrs r3, r2, #8
-    uxtb r1, r2
-
-    subs r6, r1, r0
-    blt 1f
-
-    subs r1, r2, r0
-    rsbs r0, r0, #0
-1:
-
-    muls r3, r3, r0
-    adds r2, r1, r3
-
-    rsbs r3, r0, #0
-    uxtb r3, r3
-    lsrs r3, r3, #4
-    adcs r0, r0, r3
-
-    cmp r6, #0
-    blt 1f
-
-    rsbs r0, r0, #0
-1:
-
-    strb r0, [r7, r5]
-
-    lsrs r6, r6, #31
-    pop { r0, r1, r3, pc }

asm_unpackers/unpack_riscv.S

@@ -1,142 +0,0 @@
-.section .text
-
-#define FRAME_SIZE (256+32*4+4)
-
-// x8 prob array ptr
-// x9 prev was literal
-// x10 out ptr
-// x11 in ptr
-// x12 offset
-// x13 state
-
-.global upkr_unpack
-.type upkr_unpack, %function
-upkr_unpack:
-	mv t4, ra
-	mv x17, x8
-	mv t6, x9
-	li x13, FRAME_SIZE
-	li x9, 128
-1:
-	addi sp, sp, -1
-	sb x9, 0(sp)
-	addi x13, x13, -1
-	bnez x13, 1b
-	
-.Lmainloop:
-	li x14, 0
-	jal upkr_decode_bit
-	beqz x15, .Lliteral
-	
-	slli x14, x14, 8
-	beqz x9, .Lread_offset_inc_x14
-	jal upkr_decode_bit
-	bnez x15, .Lread_offset
-
-.Lfinished_offset:
-	addi x14, x14, 64
-	jal t3, upkr_decode_number
-1:
-	add x14, x10, t0
-	lbu x14, (x14)
-.Lstore_byte:
-	sb x14, (x10)
-	addi x10, x10, 1
-	addi x9, x9, 1
-	blt x9, x0, 1b
-	j .Lmainloop
-	
-.Lliteral:
-	jal upkr_decode_bit
-	addi x14, x14, -1
-	slli x14, x14, 1
-	add x14, x14, x15
-	srli x9, x14, 8
-	beqz x9, .Lliteral
-	j .Lstore_byte
-
-.Lread_offset_inc_x14:
-	addi x14, x14, 1
-.Lread_offset:
-	jal t3, upkr_decode_number
-	addi t0, x9, 1
-	bnez t0, .Lfinished_offset
-.Ldone:
-	addi sp, sp, FRAME_SIZE
-	mv x8, x17
-	mv x9, t6
-	jr t4
-
-// x14 context index
-// return: x9 negtive decoded number 
-upkr_decode_number:
-	mv t5, x14
-	li x9, 0
-	li x8, -1
-1:
-	jal upkr_decode_bit
-	beqz x15, 1f
-	jal upkr_decode_bit
-	beqz x15, 2f
-	add x9, x9, x8
-2:
-	slli x8, x8, 1
-	j 1b
-1:
-	add x9, x9, x8
-	
-	mv x14, t5
-	jr t3
-
-upkr_load_byte:
-	lbu x15, 0(x11)
-	addi x11, x11, 1
-	slli x13, x13, 8
-	add x13, x13, x15
-// x8 prob array ptr
-// x11 in ptr
-// x13 state
-// x14 context index
-// return:
-//   x14 context index + 1
-//   x15 decoded bit
-upkr_decode_bit:
-	srli x15, x13, 12
-	beqz x15, upkr_load_byte
-
-	mv t1, x14
-	mv t2, x10
-	
-	add x14, x14, sp
-	lbu x12, 0(x14)
-	
-	andi x10, x13, 255
-	sltu x15, x10, x12
-	srli x13, x13, 8
-	beqz x15, .Lelse
-	
-	mul x13, x13, x12
-	add x13, x13, x10
-	li x10, 256 + 8
-	sub x10, x10, x12
-	srli x10, x10, 4
-	add x12, x12, x10
-	j .Lendif
-
-.Lelse:
-	li x16, 256
-	sub x16, x16, x12
-	mul x13, x13, x16
-	add x13, x13, x10
-	sub x13, x13, x12
-	addi x10, x12, 8
-	srli x10, x10, 4
-	sub x12, x12, x10
-
-.Lendif:
-
-	sb x12, 0(x14)
-	
-	addi x14, t1, 1
-	mv x10, t2
-	ret

c_unpacker/decode_bit_alt.c

@@ -1,33 +0,0 @@
-int upkr_decode_bit(int context_index) {
-#ifdef UPKR_BITSTREAM
-    while(upkr_state < 32768) {
-        if(upkr_bits_left == 0) {
-            upkr_current_byte = *upkr_data_ptr++;
-            upkr_bits_left = 8;
-        }
-        upkr_state = (upkr_state << 1) + (upkr_current_byte & 1);
-        upkr_current_byte >>= 1;
-        --upkr_bits_left;
-    }
-#else
-    while(upkr_state < 4096) {
-        upkr_state = (upkr_state << 8) | *upkr_data_ptr++;
-    }
-#endif
-   
-    int prob = upkr_probs[context_index];
-    int bit = (upkr_state & 255) < prob ? 1 : 0;
-    
-    if(bit) {
-        prob = 256 - prob;
-    }
-    upkr_state -= prob * ((upkr_state >> 8) + (bit ^ 1));
-    prob -= (prob + 8) >> 4;
-    if(bit) {
-        prob = -prob;
-    }
-    upkr_probs[context_index] = prob;
-
-    return bit;
-}
-

c_unpacker/main.c

@@ -1,7 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-void* upkr_unpack(void* destination, void* compressed_data);
+int upkr_unpack(void* destination, void* compressed_data);
 
 int main(int argn, char** argv) {
   void* input_buffer = malloc(1024*1024);
@@ -13,8 +13,7 @@ int main(int argn, char** argv) {
   
   printf("Compressed size: %d\n", in_size);
   
-  void* end_ptr = upkr_unpack(output_buffer, input_buffer);
-  int out_size = (char*)end_ptr - (char*)output_buffer;
+  int out_size = upkr_unpack(output_buffer, input_buffer);
   
   printf("Uncompressed size: %d\n", out_size);
   

c_unpacker/unpack.c

@@ -19,8 +19,8 @@ int upkr_decode_bit(int context_index) {
             upkr_current_byte = *upkr_data_ptr++;
             upkr_bits_left = 8;
         }
-        upkr_state = (upkr_state << 1) + (upkr_current_byte & 1);
-        upkr_current_byte >>= 1;
+        upkr_state = (upkr_state << 1) + (upkr_current_byte >> 7);
+        upkr_current_byte <<= 1;
         --upkr_bits_left;
     }
 #else
@@ -30,16 +30,18 @@ int upkr_decode_bit(int context_index) {
 #endif
    
     int prob = upkr_probs[context_index];
-    int bit = (upkr_state & 255) < prob ? 1 : 0;
+    int bit = (upkr_state & 255) >= prob ? 1 : 0;
     
+    int prob_offset = 16;
+    int state_offset = 0;
+    int state_scale = prob;
     if(bit) {
-        upkr_state = prob * (upkr_state >> 8) + (upkr_state & 255);
-        prob += (256 - prob + 8) >> 4;
-    } else {
-        upkr_state = (256 - prob) * (upkr_state >> 8) + (upkr_state & 255) - prob;
-        prob -= (prob + 8) >> 4;
+        state_offset = -prob;
+        state_scale = 256 - prob;
+        prob_offset = 0;
     }
-    upkr_probs[context_index] = prob;
+    upkr_state = state_offset + state_scale * (upkr_state >> 8) + (upkr_state & 255);
+    upkr_probs[context_index] = prob_offset + prob - ((prob + 8) >> 4); 
 
     return bit;
 }
@@ -54,7 +56,7 @@ int upkr_decode_length(int context_index) {
     return length | (1 << bit_pos);
 }
 
-void* upkr_unpack(void* destination, void* compressed_data) {
+int upkr_unpack(void* destination, void* compressed_data) {
     upkr_data_ptr = (u8*)compressed_data;
     upkr_state = 0;
 #ifdef UPKR_BITSTREAM
@@ -92,5 +94,5 @@ void* upkr_unpack(void* destination, void* compressed_data) {
         }
     }
     
-    return write_ptr;
+    return write_ptr - (u8*)destination;
 }

compare-variants

@@ -0,0 +1,50 @@
+#!/bin/env ruby
+
+configs = [
+    [:master, '-b'],
+    [:z80, '-b'],
+    [:z80, ['-b', '-r']],
+    ['old-prob-update', '-b']
+]
+
+files = Dir[ARGV[0] + '/*'].select {|f| !(f =~ /\.txt$/) }
+short_names = files.map {|f| File.basename(f)[..16] }
+results = []
+
+def print_results(configs, names, results)
+    configs.each_with_index do |config, i|
+        printf "%d: %s\n", i + 1, config
+    end
+    
+    print '                '
+    configs.each_index do |i|
+        printf "  %-4d", i + 1
+    end
+    puts
+    names.each_with_index do |name, i|
+        printf "%16s", name
+        for res in results
+            res = res[i]
+            printf "  %-4s", res if res
+        end
+        puts
+    end
+end
+
+for config in configs
+    raise unless system('git', 'checkout', config[0].to_s)
+    config_results = []
+    results << config_results
+    for file in files
+        if system(*['cargo', 'run', '--release', 'pack', '-l', '9', config[1], file, '/tmp/out.upk'].flatten) &&
+            system(*['cargo', 'run', '--release', 'unpack', config[1], '/tmp/out.upk', '/tmp/out.bin'].flatten) &&
+            File.read(file) == File.read('/tmp/out.bin')
+            size = File.size('/tmp/out.upk')
+            config_results << size
+        else
+            config_results << 'ERR'
+        end
+        print_results(configs, short_names, results)
+    end
+end
+

src/context_state.rs

@@ -1,17 +1,12 @@
-use crate::{
-    rans::{ONE_PROB, PROB_BITS},
-    Config,
-};
+use crate::rans::{ONE_PROB, PROB_BITS};
 
 const INIT_PROB: u16 = 1 << (PROB_BITS - 1);
-const UPDATE_RATE: u32 = 4;
-const UPDATE_ADD: u32 = 8;
+const UPDATE_RATE: i32 = 4;
+const UPDATE_ADD: i32 = 8;
 
 #[derive(Clone)]
 pub struct ContextState {
     contexts: Vec<u8>,
-    invert_bit_encoding: bool,
-    simplified_prob_update: bool,
 }
 
 pub struct Context<'a> {
@@ -20,11 +15,9 @@ pub struct Context<'a> {
 }
 
 impl ContextState {
-    pub fn new(size: usize, config: &Config) -> ContextState {
+    pub fn new(size: usize) -> ContextState {
         ContextState {
             contexts: vec![INIT_PROB as u8; size],
-            invert_bit_encoding: config.invert_bit_encoding,
-            simplified_prob_update: config.simplified_prob_update,
         }
     }
 
@@ -40,21 +33,13 @@ impl<'a> Context<'a> {
 
     pub fn update(&mut self, bit: bool) {
         let old = self.state.contexts[self.index];
-
-        self.state.contexts[self.index] = if self.state.simplified_prob_update {
-            let offset = if bit ^ self.state.invert_bit_encoding {
-                ONE_PROB as i32 >> UPDATE_RATE
-            } else {
-                0
-            };
-
-            (offset + old as i32 - ((old as i32 + UPDATE_ADD as i32) >> UPDATE_RATE)) as u8
+        let offset = if !bit {
+            ONE_PROB as i32 >> UPDATE_RATE
         } else {
-            if bit ^ self.state.invert_bit_encoding {
-                old + ((ONE_PROB - old as u32 + UPDATE_ADD) >> UPDATE_RATE) as u8
-            } else {
-                old - ((old as u32 + UPDATE_ADD) >> UPDATE_RATE) as u8
-            }
+            0
         };
+
+        self.state.contexts[self.index] =
+            (offset + old as i32 - ((old as i32 + UPDATE_ADD) >> UPDATE_RATE)) as u8;
     }
 }

src/greedy_packer.rs

@@ -1,16 +1,16 @@
+use crate::lz;
 use crate::match_finder::MatchFinder;
 use crate::rans::RansCoder;
 use crate::ProgressCallback;
-use crate::{lz, Config};
 
 pub fn pack(
     data: &[u8],
-    config: &Config,
+    use_bitstream: bool,
     mut progress_callback: Option<ProgressCallback>,
 ) -> Vec<u8> {
     let mut match_finder = MatchFinder::new(data);
-    let mut rans_coder = RansCoder::new(config);
-    let mut state = lz::CoderState::new(config);
+    let mut rans_coder = RansCoder::new(use_bitstream);
+    let mut state = lz::CoderState::new();
 
     let mut pos = 0;
     while pos < data.len() {
@@ -26,7 +26,7 @@ pub fn pack(
                     offset: offset as u32,
                     len: m.length as u32,
                 }
-                .encode(&mut rans_coder, &mut state, config);
+                .encode(&mut rans_coder, &mut state);
                 pos += m.length;
                 encoded_match = true;
             }
@@ -45,7 +45,7 @@ pub fn pack(
                         offset: offset as u32,
                         len: length as u32,
                     }
-                    .encode(&mut rans_coder, &mut state, config);
+                    .encode(&mut rans_coder, &mut state);
                     pos += length;
                     encoded_match = true;
                 }
@@ -53,11 +53,11 @@ pub fn pack(
         }
 
         if !encoded_match {
-            lz::Op::Literal(data[pos]).encode(&mut rans_coder, &mut state, config);
+            lz::Op::Literal(data[pos]).encode(&mut rans_coder, &mut state);
             pos += 1;
         }
     }
 
-    lz::encode_eof(&mut rans_coder, &mut state, config);
+    lz::encode_eof(&mut rans_coder, &mut state);
     rans_coder.finish()
 }

src/lib.rs

@@ -9,46 +9,16 @@ pub use lz::unpack;
 
 pub type ProgressCallback<'a> = &'a mut dyn FnMut(usize);
 
-pub struct Config {
-    pub use_bitstream: bool,
-    pub parity_contexts: usize,
-
-    pub invert_bit_encoding: bool,
-    pub is_match_bit: bool,
-    pub new_offset_bit: bool,
-    pub continue_value_bit: bool,
-
-    pub bitstream_is_big_endian: bool,
-    pub simplified_prob_update: bool,
-}
-
-impl Default for Config {
-    fn default() -> Config {
-        Config {
-            use_bitstream: false,
-            parity_contexts: 1,
-
-            invert_bit_encoding: false,
-            is_match_bit: true,
-            new_offset_bit: true,
-            continue_value_bit: true,
-
-            bitstream_is_big_endian: false,
-            simplified_prob_update: false,
-        }
-    }
-}
-
 pub fn pack(
     data: &[u8],
     level: u8,
-    config: Config,
+    use_bitstream: bool,
     progress_callback: Option<ProgressCallback>,
 ) -> Vec<u8> {
     if level == 0 {
-        greedy_packer::pack(data, &config, progress_callback)
+        greedy_packer::pack(data, use_bitstream, progress_callback)
     } else {
-        parsing_packer::pack(data, level, &config, progress_callback)
+        parsing_packer::pack(data, level, use_bitstream, progress_callback)
     }
 }
 

src/lz.rs

@@ -1,6 +1,5 @@
 use crate::context_state::ContextState;
 use crate::rans::{EntropyCoder, RansDecoder};
-use crate::Config;
 
 #[derive(Copy, Clone, Debug)]
 pub enum Op {
@@ -9,66 +8,42 @@ pub enum Op {
 }
 
 impl Op {
-    pub fn encode(&self, coder: &mut dyn EntropyCoder, state: &mut CoderState, config: &Config) {
-        let literal_base = state.pos % state.parity_contexts * 256;
+    pub fn encode(&self, coder: &mut dyn EntropyCoder, state: &mut CoderState) {
         match self {
             &Op::Literal(lit) => {
-                encode_bit(coder, state, literal_base, !config.is_match_bit);
+                encode_bit(coder, state, 0, false);
                 let mut context_index = 1;
                 for i in (0..8).rev() {
                     let bit = (lit >> i) & 1 != 0;
-                    encode_bit(coder, state, literal_base + context_index, bit);
+                    encode_bit(coder, state, context_index, bit);
                     context_index = (context_index << 1) | bit as usize;
                 }
                 state.prev_was_match = false;
-                state.pos += 1;
             }
             &Op::Match { offset, len } => {
-                encode_bit(coder, state, literal_base, config.is_match_bit);
+                encode_bit(coder, state, 0, true);
                 if !state.prev_was_match {
-                    encode_bit(
-                        coder,
-                        state,
-                        256 * state.parity_contexts,
-                        (offset != state.last_offset) == config.new_offset_bit,
-                    );
+                    encode_bit(coder, state, 256, offset != state.last_offset);
                 } else {
                     assert!(offset != state.last_offset);
                 }
                 if offset != state.last_offset {
-                    encode_length(
-                        coder,
-                        state,
-                        256 * state.parity_contexts + 1,
-                        offset + 1,
-                        config,
-                    );
+                    encode_length(coder, state, 257, offset + 1);
                     state.last_offset = offset;
                 }
-                encode_length(coder, state, 256 * state.parity_contexts + 65, len, config);
+                encode_length(coder, state, 257 + 64, len);
                 state.prev_was_match = true;
-                state.pos += len as usize;
             }
         }
     }
 }
 
-pub fn encode_eof(coder: &mut dyn EntropyCoder, state: &mut CoderState, config: &Config) {
-    encode_bit(
-        coder,
-        state,
-        state.pos % state.parity_contexts * 256,
-        config.is_match_bit,
-    );
+pub fn encode_eof(coder: &mut dyn EntropyCoder, state: &mut CoderState) {
+    encode_bit(coder, state, 0, true);
     if !state.prev_was_match {
-        encode_bit(
-            coder,
-            state,
-            256 * state.parity_contexts,
-            config.new_offset_bit,
-        );
+        encode_bit(coder, state, 256, true);
     }
-    encode_length(coder, state, 256 * state.parity_contexts + 1, 1, config);
+    encode_length(coder, state, 257, 1);
 }
 
 fn encode_bit(
@@ -85,18 +60,17 @@ fn encode_length(
     state: &mut CoderState,
     context_start: usize,
     mut value: u32,
-    config: &Config,
 ) {
     assert!(value >= 1);
 
     let mut context_index = context_start;
     while value >= 2 {
-        encode_bit(coder, state, context_index, config.continue_value_bit);
+        encode_bit(coder, state, context_index, true);
         encode_bit(coder, state, context_index + 1, value & 1 != 0);
         context_index += 2;
         value >>= 1;
     }
-    encode_bit(coder, state, context_index, !config.continue_value_bit);
+    encode_bit(coder, state, context_index, false);
 }
 
 #[derive(Clone)]
@@ -104,18 +78,14 @@ pub struct CoderState {
     contexts: ContextState,
     last_offset: u32,
     prev_was_match: bool,
-    pos: usize,
-    parity_contexts: usize,
 }
 
 impl CoderState {
-    pub fn new(config: &Config) -> CoderState {
+    pub fn new() -> CoderState {
         CoderState {
-            contexts: ContextState::new((1 + 255) * config.parity_contexts + 1 + 64 + 64, config),
+            contexts: ContextState::new(1 + 255 + 1 + 64 + 64),
             last_offset: 0,
             prev_was_match: false,
-            pos: 0,
-            parity_contexts: config.parity_contexts,
         }
     }
 
@@ -124,9 +94,9 @@ impl CoderState {
     }
 }
 
-pub fn unpack(packed_data: &[u8], config: Config) -> Vec<u8> {
-    let mut decoder = RansDecoder::new(packed_data, &config);
-    let mut contexts = ContextState::new((1 + 255) * config.parity_contexts + 1 + 64 + 64, &config);
+pub fn unpack(packed_data: &[u8], use_bitstream: bool) -> Vec<u8> {
+    let mut decoder = RansDecoder::new(packed_data, use_bitstream);
+    let mut contexts = ContextState::new(1 + 255 + 1 + 64 + 64);
     let mut result = vec![];
     let mut offset = 0;
     let mut prev_was_match = false;
@@ -135,13 +105,10 @@ pub fn unpack(packed_data: &[u8], config: Config) -> Vec<u8> {
         decoder: &mut RansDecoder,
         contexts: &mut ContextState,
         mut context_index: usize,
-        config: &Config,
     ) -> usize {
         let mut length = 0;
         let mut bit_pos = 0;
-        while decoder.decode_with_context(&mut contexts.context_mut(context_index))
-            == config.continue_value_bit
-        {
+        while decoder.decode_with_context(&mut contexts.context_mut(context_index)) {
             length |= (decoder.decode_with_context(&mut contexts.context_mut(context_index + 1))
                 as usize)
                 << bit_pos;
@@ -152,31 +119,14 @@ pub fn unpack(packed_data: &[u8], config: Config) -> Vec<u8> {
     }
 
     loop {
-        let literal_base = result.len() % config.parity_contexts * 256;
-        if decoder.decode_with_context(&mut contexts.context_mut(literal_base))
-            == config.is_match_bit
-        {
-            if prev_was_match
-                || decoder
-                    .decode_with_context(&mut contexts.context_mut(256 * config.parity_contexts))
-                    == config.new_offset_bit
-            {
-                offset = decode_length(
-                    &mut decoder,
-                    &mut contexts,
-                    256 * config.parity_contexts + 1,
-                    &config,
-                ) - 1;
+        if decoder.decode_with_context(&mut contexts.context_mut(0)) {
+            if prev_was_match || decoder.decode_with_context(&mut contexts.context_mut(256)) {
+                offset = decode_length(&mut decoder, &mut contexts, 257) - 1;
                 if offset == 0 {
                     break;
                 }
             }
-            let length = decode_length(
-                &mut decoder,
-                &mut contexts,
-                256 * config.parity_contexts + 65,
-                &config,
-            );
+            let length = decode_length(&mut decoder, &mut contexts, 257 + 64);
             for _ in 0..length {
                 result.push(result[result.len() - offset]);
             }
@@ -185,8 +135,7 @@ pub fn unpack(packed_data: &[u8], config: Config) -> Vec<u8> {
             let mut context_index = 1;
             let mut byte = 0;
             for i in (0..8).rev() {
-                let bit = decoder
-                    .decode_with_context(&mut contexts.context_mut(literal_base + context_index));
+                let bit = decoder.decode_with_context(&mut contexts.context_mut(context_index));
                 context_index = (context_index << 1) | bit as usize;
                 byte |= (bit as u8) << i;
             }

src/main.rs

@@ -1,149 +1,82 @@
-use anyhow::Result;
-use std::ffi::OsStr;
+use anyhow::{bail, Result};
 use std::io::prelude::*;
-use std::process;
 use std::{fs::File, path::PathBuf};
 
 fn main() -> Result<()> {
-    let mut config = upkr::Config::default();
-    let mut reverse = false;
-    let mut unpack = false;
-    let mut level = 2;
-    let mut infile: Option<PathBuf> = None;
-    let mut outfile: Option<PathBuf> = None;
+    let mut args = pico_args::Arguments::from_env();
 
-    let mut parser = lexopt::Parser::from_env();
-    while let Some(arg) = parser.next()? {
-        use lexopt::prelude::*;
-        match arg {
-            Short('b') | Long("bitstream") => config.use_bitstream = true,
-            Short('p') | Long("parity") => config.parity_contexts = parser.value()?.parse()?,
-            Short('r') | Long("reverse") => reverse = true,
-            Long("invert-is-match-bit") => config.is_match_bit = false,
-            Long("invert-new-offset-bit") => config.new_offset_bit = false,
-            Long("invert-continue-value-bit") => config.continue_value_bit = false,
-            Long("invert-bit-encoding") => config.invert_bit_encoding = true,
-            Long("simplified-prob-update") => config.simplified_prob_update = true,
-            Long("big-endian-bitstream") => {
-                config.use_bitstream = true;
-                config.bitstream_is_big_endian = true;
+    match args.subcommand()?.as_ref().map(|s| s.as_str()) {
+        None => print_help(),
+        Some("pack") => {
+            let level = args.opt_value_from_str(["-l", "--level"])?.unwrap_or(2u8);
+            let use_bitstream = args.contains(["-b", "--bitstream"]);
+            let reverse = args.contains(["-r", "--reverse"]);
+
+            let infile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
+            let outfile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
+
+            let mut data = vec![];
+            File::open(infile)?.read_to_end(&mut data)?;
+            if reverse {
+                data.reverse();
             }
 
-            Long("z80") => {
-                config.use_bitstream = true;
-                config.bitstream_is_big_endian = true;
-                config.invert_bit_encoding = true;
-                config.simplified_prob_update = true;
-            }
-            Long("x86") => {
-                config.use_bitstream = true;
-                config.continue_value_bit = false;
-                config.is_match_bit = false;
+            let mut pb = pbr::ProgressBar::new(data.len() as u64);
+            pb.set_units(pbr::Units::Bytes);
+            let mut packed_data = upkr::pack(
+                &data,
+                level,
+                use_bitstream,
+                Some(&mut |pos| {
+                    pb.set(pos as u64);
+                }),
+            );
+            pb.finish();
+
+            if reverse {
+                packed_data.reverse();
             }
 
-            Short('u') | Long("unpack") => unpack = true,
-            Short('l') | Long("level") => level = parser.value()?.parse()?,
-            Short('h') | Long("help") => print_help(0),
-            Value(val) if infile.is_none() => infile = Some(val.try_into()?),
-            Value(val) if outfile.is_none() => outfile = Some(val.try_into()?),
-            _ => return Err(arg.unexpected().into()),
+            println!(
+                "Compressed {} bytes to {} bytes ({}%)",
+                data.len(),
+                packed_data.len(),
+                packed_data.len() as f32 * 100. / data.len() as f32
+            );
+            File::create(outfile)?.write_all(&packed_data)?;
         }
-    }
+        Some("unpack") => {
+            let use_bitstream = args.contains(["-b", "--bitstream"]);
+            let reverse = args.contains(["-r", "--reverse"]);
 
-    let infile = infile.unwrap_or_else(|| print_help(1));
-    let outfile = outfile.unwrap_or_else(|| {
-        let mut name = infile.clone();
-        if unpack {
-            if name.extension().filter(|&e| e == "upk").is_some() {
-                name.set_extension("");
-            } else {
-                name.set_extension("bin");
+            let infile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
+            let outfile = args.free_from_os_str::<PathBuf, bool>(|s| Ok(s.into()))?;
+
+            let mut data = vec![];
+            File::open(infile)?.read_to_end(&mut data)?;
+            if reverse {
+                data.reverse();
             }
-        } else {
-            let mut filename = name
-                .file_name()
-                .unwrap_or_else(|| OsStr::new(""))
-                .to_os_string();
-            filename.push(".upk");
-            name.set_file_name(filename);
+            let mut unpacked_data = upkr::unpack(&data, use_bitstream);
+            if reverse {
+                unpacked_data.reverse();
+            }
+            File::create(outfile)?.write_all(&unpacked_data)?;
         }
-        name
-    });
-
-    if config.parity_contexts != 1 && config.parity_contexts != 2 && config.parity_contexts != 4 {
-        eprintln!("--parity has to be 1, 2, or 4");
-        process::exit(1);
-    }
-
-    if !unpack {
-        let mut data = vec![];
-        File::open(infile)?.read_to_end(&mut data)?;
-        if reverse {
-            data.reverse();
+        Some(other) => {
+            bail!("Unknown subcommand '{}'", other);
         }
-
-        let mut pb = pbr::ProgressBar::new(data.len() as u64);
-        pb.set_units(pbr::Units::Bytes);
-        let mut packed_data = upkr::pack(
-            &data,
-            level,
-            config,
-            Some(&mut |pos| {
-                pb.set(pos as u64);
-            }),
-        );
-        pb.finish();
-
-        if reverse {
-            packed_data.reverse();
-        }
-
-        println!(
-            "Compressed {} bytes to {} bytes ({}%)",
-            data.len(),
-            packed_data.len(),
-            packed_data.len() as f32 * 100. / data.len() as f32
-        );
-        File::create(outfile)?.write_all(&packed_data)?;
-    } else {
-        let mut data = vec![];
-        File::open(infile)?.read_to_end(&mut data)?;
-        if reverse {
-            data.reverse();
-        }
-        let mut unpacked_data = upkr::unpack(&data, config);
-        if reverse {
-            unpacked_data.reverse();
-        }
-        File::create(outfile)?.write_all(&unpacked_data)?;
     }
 
     Ok(())
 }
 
-fn print_help(exit_code: i32) -> ! {
+fn print_help() {
     eprintln!("Usage:");
-    eprintln!("  upkr [-l level(0-9)] [config options] <infile> [<outfile>]");
-    eprintln!("  upkr -u [config options] <infile> [<outfile>]");
+    eprintln!("  upkr pack [-b] [-l level(0-9)] <infile> <outfile>");
+    eprintln!("  upkr unpack [-b] <infile> <outfile>");
     eprintln!();
-    eprintln!(" -l, --level N       compression level 0-9");
-    eprintln!(" -u, --unpack        unpack infile");
-    eprintln!();
-    eprintln!("Config presets for specific unpackers:");
-    eprintln!(" --z80               --big-endian-bitstream --invert-bit-encoding --simplified-prob-update");
-    eprintln!(" --x86               --bitstream --invert-is-match-bit --invert-continue-value-bit");
-    eprintln!();
-    eprintln!("Config options (need to match when packing/unpacking):");
     eprintln!(" -b, --bitstream     bitstream mode");
-    eprintln!(" -p, --parity N      use N (2/4) parity contexts");
-    eprintln!(" -r, --reverse       reverse input & output");
-    eprintln!();
-    eprintln!("Config options to tailor output to specific optimized unpackers:");
-    eprintln!(" --invert-is-match-bit");
-    eprintln!(" --invert-new-offset-bit");
-    eprintln!(" --invert-continue-value-bit");
-    eprintln!(" --invert-bit-encoding");
-    eprintln!(" --simplified-prob-update");
-    eprintln!(" --big-endian-bitstream   (implies --bitstream)");
-    process::exit(exit_code);
+    eprintln!(" -l, --level N       compression level 0-9");
+    std::process::exit(1);
 }

src/parsing_packer.rs

@@ -6,24 +6,19 @@ use crate::match_finder::MatchFinder;
 use crate::rans::{CostCounter, RansCoder};
 use crate::{lz, ProgressCallback};
 
-pub fn pack(
-    data: &[u8],
-    level: u8,
-    config: &crate::Config,
-    progress_cb: Option<ProgressCallback>,
-) -> Vec<u8> {
-    let mut parse = parse(data, Config::from_level(level), config, progress_cb);
+pub fn pack(data: &[u8], level: u8, use_bitstream: bool, progress_cb: Option<ProgressCallback>) -> Vec<u8> {
+    let mut parse = parse(data, Config::from_level(level), progress_cb);
     let mut ops = vec![];
     while let Some(link) = parse {
         ops.push(link.op);
         parse = link.prev.clone();
     }
-    let mut state = lz::CoderState::new(config);
-    let mut coder = RansCoder::new(config);
+    let mut state = lz::CoderState::new();
+    let mut coder = RansCoder::new(use_bitstream);
     for op in ops.into_iter().rev() {
-        op.encode(&mut coder, &mut state, config);
+        op.encode(&mut coder, &mut state);
     }
-    lz::encode_eof(&mut coder, &mut state, config);
+    lz::encode_eof(&mut coder, &mut state);
     coder.finish()
 }
 
@@ -43,7 +38,6 @@ type Arrivals = HashMap<usize, Vec<Arrival>>;
 fn parse(
     data: &[u8],
     config: Config,
-    encoding_config: &crate::Config,
     mut progress_cb: Option<ProgressCallback>,
 ) -> Option<Rc<Parse>> {
     let mut match_finder = MatchFinder::new(data)
@@ -108,7 +102,6 @@ fn parse(
         length: usize,
         arrival: &Arrival,
         max_arrivals: usize,
-        config: &crate::Config,
     ) {
         cost_counter.reset();
         let mut state = arrival.state.clone();
@@ -116,7 +109,7 @@ fn parse(
             offset: offset as u32,
             len: length as u32,
         };
-        op.encode(cost_counter, &mut state, config);
+        op.encode(cost_counter, &mut state);
         add_arrival(
             arrivals,
             pos + length,
@@ -136,13 +129,13 @@ fn parse(
         0,
         Arrival {
             parse: None,
-            state: lz::CoderState::new(encoding_config),
+            state: lz::CoderState::new(),
             cost: 0.0,
         },
         max_arrivals,
     );
 
-    let cost_counter = &mut CostCounter::new(encoding_config);
+    let cost_counter = &mut CostCounter::new();
     let mut best_per_offset = HashMap::new();
     for pos in 0..data.len() {
         let match_length = |offset: usize| {
@@ -192,7 +185,6 @@ fn parse(
                     m.length,
                     &arrival,
                     max_arrivals,
-                    encoding_config,
                 );
                 if m.length >= config.greedy_size {
                     break 'arrival_loop;
@@ -216,7 +208,6 @@ fn parse(
                     length,
                     &arrival,
                     max_arrivals,
-                    encoding_config,
                 );
                 found_last_offset |= offset as u32 == arrival.state.last_offset();
                 if offset < near_matches.len() {
@@ -237,7 +228,6 @@ fn parse(
                         length,
                         &arrival,
                         max_arrivals,
-                        encoding_config,
                     );
                 }
             }
@@ -245,7 +235,7 @@ fn parse(
             cost_counter.reset();
             let mut state = arrival.state;
             let op = lz::Op::Literal(data[pos]);
-            op.encode(cost_counter, &mut state, encoding_config);
+            op.encode(cost_counter, &mut state);
             add_arrival(
                 &mut arrivals,
                 pos + 1,

src/rans.rs

@@ -1,4 +1,4 @@
-use crate::{context_state::Context, Config};
+use crate::context_state::Context;
 
 pub const PROB_BITS: u32 = 8;
 pub const ONE_PROB: u32 = 1 << PROB_BITS;
@@ -15,25 +15,20 @@ pub trait EntropyCoder {
 pub struct RansCoder {
     bits: Vec<u16>,
     use_bitstream: bool,
-    bitstream_is_big_endian: bool,
-    invert_bit_encoding: bool,
 }
 
 impl EntropyCoder for RansCoder {
     fn encode_bit(&mut self, bit: bool, prob: u16) {
         assert!(prob < 32768);
-        self.bits
-            .push(prob | (((bit ^ self.invert_bit_encoding) as u16) << 15));
+        self.bits.push(prob | ((bit as u16) << 15));
     }
 }
 
 impl RansCoder {
-    pub fn new(config: &Config) -> RansCoder {
+    pub fn new(use_bitstream: bool) -> RansCoder {
         RansCoder {
             bits: Vec::new(),
-            use_bitstream: config.use_bitstream,
-            bitstream_is_big_endian: config.bitstream_is_big_endian,
-            invert_bit_encoding: config.invert_bit_encoding,
+            use_bitstream,
         }
     }
 
@@ -43,31 +38,18 @@ impl RansCoder {
         let mut state = 1 << l_bits;
 
         let mut byte = 0u8;
-        let mut bit = if self.bitstream_is_big_endian { 0 } else { 8 };
+        let mut bit = 0;
         let mut flush_state: Box<dyn FnMut(&mut u32)> = if self.use_bitstream {
-            if self.bitstream_is_big_endian {
-                Box::new(|state: &mut u32| {
-                    byte |= ((*state & 1) as u8) << bit;
-                    bit += 1;
-                    if bit == 8 {
-                        buffer.push(byte);
-                        byte = 0;
-                        bit = 0;
-                    }
-                    *state >>= 1;
-                })
-            } else {
-                Box::new(|state: &mut u32| {
-                    bit -= 1;
-                    byte |= ((*state & 1) as u8) << bit;
-                    if bit == 0 {
-                        buffer.push(byte);
-                        byte = 0;
-                        bit = 8;
-                    }
-                    *state >>= 1;
-                })
-            }
+            Box::new(|state: &mut u32| {
+                byte |= ((*state & 1) as u8) << bit;
+                bit += 1;
+                if bit == 8 {
+                    buffer.push(byte);
+                    byte = 0;
+                    bit = 0;
+                }
+                *state >>= 1;
+            })
         } else {
             Box::new(|state: &mut u32| {
                 buffer.push(*state as u8);
@@ -79,7 +61,7 @@ impl RansCoder {
         let max_state_factor: u32 = 1 << (l_bits + num_flush_bits - PROB_BITS);
         for step in self.bits.into_iter().rev() {
             let prob = step as u32 & 32767;
-            let (start, prob) = if step & 32768 != 0 {
+            let (start, prob) = if step & 32768 == 0 {
                 (0, prob)
             } else {
                 (prob, ONE_PROB - prob)
@@ -109,11 +91,10 @@ impl RansCoder {
 pub struct CostCounter {
     cost: f64,
     log2_table: Vec<f64>,
-    invert_bit_encoding: bool,
 }
 
 impl CostCounter {
-    pub fn new(config: &Config) -> CostCounter {
+    pub fn new() -> CostCounter {
         let log2_table = (0..ONE_PROB)
             .map(|prob| {
                 let inv_prob = ONE_PROB as f64 / prob as f64;
@@ -123,7 +104,6 @@ impl CostCounter {
         CostCounter {
             cost: 0.0,
             log2_table,
-            invert_bit_encoding: config.invert_bit_encoding,
         }
     }
 
@@ -138,7 +118,7 @@ impl CostCounter {
 
 impl EntropyCoder for CostCounter {
     fn encode_bit(&mut self, bit: bool, prob: u16) {
-        let prob = if bit ^ self.invert_bit_encoding {
+        let prob = if !bit {
             prob as u32
         } else {
             ONE_PROB - prob as u32
@@ -153,22 +133,18 @@ pub struct RansDecoder<'a> {
     use_bitstream: bool,
     byte: u8,
     bits_left: u8,
-    invert_bit_encoding: bool,
-    bitstream_is_big_endian: bool,
 }
 
 const PROB_MASK: u32 = ONE_PROB - 1;
 
 impl<'a> RansDecoder<'a> {
-    pub fn new(data: &'a [u8], config: &Config) -> RansDecoder<'a> {
+    pub fn new(data: &'a [u8], use_bitstream: bool) -> RansDecoder<'a> {
         RansDecoder {
             data,
             state: 0,
-            use_bitstream: config.use_bitstream,
+            use_bitstream,
             byte: 0,
             bits_left: 0,
-            invert_bit_encoding: config.invert_bit_encoding,
-            bitstream_is_big_endian: config.bitstream_is_big_endian,
         }
     }
 
@@ -187,13 +163,8 @@ impl<'a> RansDecoder<'a> {
                     self.data = &self.data[1..];
                     self.bits_left = 8;
                 }
-                if self.bitstream_is_big_endian {
-                    self.state = (self.state << 1) | (self.byte >> 7) as u32;
-                    self.byte <<= 1;
-                } else {
-                    self.state = (self.state << 1) | (self.byte & 1) as u32;
-                    self.byte >>= 1;
-                }
+                self.state = (self.state << 1) | (self.byte >> 7) as u32;
+                self.byte <<= 1;
                 self.bits_left -= 1;
             }
         } else {
@@ -203,15 +174,15 @@ impl<'a> RansDecoder<'a> {
             }
         }
 
-        let bit = (self.state & PROB_MASK) < prob;
+        let bit = (self.state & PROB_MASK) >= prob;
 
         let (start, prob) = if bit {
-            (0, prob)
-        } else {
             (prob, ONE_PROB - prob)
+        } else {
+            (0, prob)
         };
         self.state = prob * (self.state >> PROB_BITS) + (self.state & PROB_MASK) - start;
 
-        bit ^ self.invert_bit_encoding
+        bit
     }
 }

z80_unpacker/.gitignore

@@ -0,0 +1,3 @@
+*.bin
+*.tap
+*.lst

z80_unpacker/Makefile

@@ -0,0 +1,11 @@
+all: unpack.bin example/example.sna
+
+# binary is positioned from ORG 0, not usable, just assembling to verify the syntax
+unpack.bin: unpack.asm
+	sjasmplus --msg=war --lst --lstlab=sort --raw=unpack.bin unpack.asm
+
+example/example.sna: unpack.asm example/example.asm
+	cd example && sjasmplus --msg=war --lst --lstlab=sort example.asm
+
+clean:
+	$(RM) unpack.bin unpack.lst example/example.sna example/example.lst

z80_unpacker/example/example.asm

@@ -0,0 +1,100 @@
+;; Example using upkr depacker for screens slideshow
+    OPT --syntax=abf
+    DEVICE ZXSPECTRUM48,$8FFF
+
+    ORG     $9000
+  ;; forward example data
+compressed_scr_files.fwd:               ; border color byte + upkr-packed .scr file
+    DB      1
+    INCBIN  "screens/Grongy - ZX Spectrum (2022).scr.upk"
+    DB      7
+    INCBIN  "screens/Schafft - Poison (2017).scr.upk"
+    DB      0
+    INCBIN  "screens/diver - Mercenary 4. The Heaven's Devil (2014) (Forever 2014 Olympic Edition, 1).scr.upk"
+    DB      6
+    INCBIN  "screens/diver - Back to Bjork (2015).scr.upk"
+.e:
+  ;; backward example data (unpacker goes from the end of the data!)
+compressed_scr_files.rwd.e: EQU $-1     ; the final IX will point one byte ahead of "$" here
+    INCBIN  "screens.reversed/diver - Back to Bjork (2015).scr.upk"
+    DB      6
+    INCBIN  "screens.reversed/diver - Mercenary 4. The Heaven's Devil (2014) (Forever 2014 Olympic Edition, 1).scr.upk"
+    DB      0
+    INCBIN  "screens.reversed/Schafft - Poison (2017).scr.upk"
+    DB      7
+    INCBIN  "screens.reversed/Grongy - ZX Spectrum (2022).scr.upk"
+compressed_scr_files.rwd:               ; border color byte + upkr-packed .scr file (backward)
+    DB      1
+
+start:
+    di
+;     OPT --zxnext
+;     nextreg 7,3                       ; ZX Next: switch to 28Mhz
+
+  ;;; FORWARD packed/unpacked data demo
+    ld      ix,compressed_scr_files.fwd
+.slideshow_loop.fwd:
+  ; set BORDER for next image
+    ld      a,(ix)
+    inc     ix
+    out     (254),a
+  ; call unpack of next image directly into VRAM
+    ld      de,$4000                    ; target VRAM
+    exx
+  ; IX = packed data, DE' = destination ($4000)
+  ; returned IX will point right after the packed data
+    call    fwd.upkr.unpack
+  ; do some busy loop with CPU to delay between images
+    call    delay
+  ; check if all images were displayed, loop around from first one then
+    ld      a,ixl
+    cp      low compressed_scr_files.fwd.e
+    jr      nz,.slideshow_loop.fwd
+
+  ;;; BACKWARD packed/unpacked data demo
+    ld      ix,compressed_scr_files.rwd
+.slideshow_loop.rwd:
+  ; set BORDER for next image
+    ld      a,(ix)
+    dec     ix
+    out     (254),a
+  ; call unpack of next image directly into VRAM
+    ld      de,$5AFF                    ; target VRAM
+    exx
+  ; IX = packed data, DE' = destination
+  ; returned IX will point right ahead of the packed data
+    call    rwd.upkr.unpack
+  ; do some busy loop with CPU to delay between images
+    call    delay
+  ; check if all images were displayed, loop around from first one then
+    ld      a,ixl
+    cp      low compressed_scr_files.rwd.e
+    jr      nz,.slideshow_loop.rwd
+
+    jr      start
+
+delay:
+    ld      bc,$AA00
+.delay:
+    .8 ex      (sp),ix
+    dec     c
+    jr      nz,.delay
+    djnz    .delay
+    ret
+
+  ; include the depacker library, optionally putting probs array buffer near end of RAM
+    DEFINE  UPKR_PROBS_ORIGIN $FA00   ; if not defined, array will be put after unpack code
+
+    MODULE fwd
+        INCLUDE "../unpack.asm"
+    ENDMODULE
+
+    MODULE rwd
+        DEFINE BACKWARDS_UNPACK         ; defined to build backwards unpack
+                ; initial IX points at last byte of compressed data
+                ; initial DE' points at last byte of unpacked data
+
+        INCLUDE "../unpack.asm"
+    ENDMODULE
+
+    SAVESNA "example.sna",start

z80_unpacker/readme.txt

@@ -0,0 +1,19 @@
+Z80 asm implementation of C unpacker, code-size focused (not performance).
+
+**ONLY BITSTREAM** variant is currently supported, make sure to use "-b" in packer.
+
+The project is expected to further evolve, including possible changes to binary format, this is
+initial version of Z80 unpacker to explore if/how it works and how it can be improved further.
+
+(copy full packer+depacker source to your project if you plan to use it, as future revisions
+may be incompatible with files you will produce with current version)
+
+Asm syntax is z00m's sjasmplus: https://github.com/z00m128/sjasmplus
+
+TODO:
+- build base corpus of test data to benchmark future changes in algorithm/format
+- review first implementation to identify weak spots where the implementation can be shorter+faster
+with acceptable small changes to the format
+- review non-bitstream variant, if it's feasible to try to implement it with Z80
+- (@ped7g) Z80N version of unpacker for ZX Next devs
+- (@exoticorn) add Z80 specific packer (to avoid confusion with original MicroW8 variant), and land it all to master branch, maybe in "z80" directory or something? (and overall decide how to organise+merge this upstream into main repo)

z80_unpacker/unpack.asm

@@ -0,0 +1,328 @@
+;; https://github.com/exoticorn/upkr/blob/z80/c_unpacker/unpack.c - original C implementation
+;; C source in comments ahead of asm - the C macros are removed to keep only bitstream variant
+;;
+;; initial version by Peter "Ped" Helcmanovsky (C) 2022, licensed same as upkr project ("unlicensed")
+;; to assemble use z00m's sjasmplus: https://github.com/z00m128/sjasmplus
+;;
+;; you can define UPKR_PROBS_ORIGIN to specific 256 byte aligned address for probs array (386 bytes),
+;; otherwise it will be positioned after the unpacker code (256 aligned)
+;;
+;; public API:
+;;
+;;     upkr.unpack
+;;         IN: IX = packed data, DE' (shadow DE) = destination
+;;         OUT: IX = after packed data
+;;         modifies: all registers except IY, requires 10 bytes of stack space
+;;
+
+;     DEFINE BACKWARDS_UNPACK         ; uncomment to build backwards depacker
+            ; initial IX points at last byte of compressed data
+            ; initial DE' points at last byte of unpacked data
+
+;     DEFINE UPKR_UNPACK_SPEED        ; uncomment to get larger but faster unpack routine
+
+    OPT push reset --syntax=abf
+    MODULE upkr
+
+NUMBER_BITS     EQU     16+15       ; context-bits per offset/length (16+15 for 16bit offsets/pointers)
+    ; numbers (offsets/lengths) are encoded like: 1a1b1c1d1e0 = 0000'0000'001e'dbca
+
+/*
+u8* upkr_data_ptr;
+u8 upkr_probs[1 + 255 + 1 + 2*32 + 2*32];
+u16 upkr_state;
+u8 upkr_current_byte;
+int upkr_bits_left;
+
+int upkr_unpack(void* destination, void* compressed_data) {
+    upkr_data_ptr = (u8*)compressed_data;
+    upkr_state = 0;
+    upkr_bits_left = 0;
+    for(int i = 0; i < sizeof(upkr_probs); ++i)
+        upkr_probs[i] = 128;
+
+    u8* write_ptr = (u8*)destination;
+
+    int prev_was_match = 0;
+    int offset = 0;
+    for(;;) {
+        if(upkr_decode_bit(0)) {
+            if(prev_was_match || upkr_decode_bit(256)) {
+                offset = upkr_decode_length(257) - 1;
+                if(offset == 0) {
+                    break;
+                }
+            }
+            int length = upkr_decode_length(257 + 64);
+            while(length--) {
+                *write_ptr = write_ptr[-offset];
+                ++write_ptr;
+            }
+            prev_was_match = 1;
+        } else {
+            int byte = 1;
+            while(byte < 256) {
+                int bit = upkr_decode_bit(byte);
+                byte = (byte << 1) + bit;
+            }
+            *write_ptr++ = byte;
+            prev_was_match = 0;
+        }
+    }
+
+    return write_ptr - (u8*)destination;
+}
+*/
+; IN: IX = compressed_data, DE' = destination
+unpack:
+  ; ** reset probs to 0x80, also reset HL (state) to zero, and set BC to probs+context 0
+    ld      hl,probs.c>>1
+    ld      bc,probs.e
+    ld      a,$80
+.reset_probs:
+    dec     bc
+    ld      (bc),a              ; will overwrite one extra byte after the array because of odd length
+    dec     bc
+    ld      (bc),a
+    dec     l
+    jr      nz,.reset_probs
+    exa
+    ; BC = probs (context_index 0), state HL = 0, A' = 0x80 (no source bits left in upkr_current_byte)
+
+  ; ** main loop to decompress data
+    ; D = prev_was_match = uninitialised, literal is expected first => will reset D to "false"
+    ; values for false/true of prev_was_match are: false = high(probs), true = 1 + high(probs)
+.decompress_data:
+    ld      c,0
+    call    decode_bit          ; if(upkr_decode_bit(0))
+    jr      c,.copy_chunk
+
+  ; * extract byte from compressed data (literal)
+    inc     c                   ; C = byte = 1 (and also context_index)
+.decode_byte:
+    call    decode_bit          ; bit = upkr_decode_bit(byte);
+    rl      c                   ; byte = (byte << 1) + bit;
+    jr      nc,.decode_byte     ; while(byte < 256)
+    ld      a,c
+    exx
+    ld      (de),a              ; *write_ptr++ = byte;
+    IFNDEF BACKWARDS_UNPACK : inc de : ELSE : dec de : ENDIF
+    exx
+    ld      d,b                 ; prev_was_match = false
+    jr      .decompress_data
+
+  ; * copy chunk of already decompressed data (match)
+.copy_chunk:
+    ld      a,b
+    inc     b                   ; context_index = 256
+        ;             if(prev_was_match || upkr_decode_bit(256)) {
+        ;                 offset = upkr_decode_length(257) - 1;
+        ;                 if (0 == offset) break;
+        ;             }
+    cp      d                   ; CF = prev_was_match
+    call    nc,decode_bit       ; if not prev_was_match, then upkr_decode_bit(256)
+    jr      nc,.keep_offset     ; if neither, keep old offset
+    inc     c                   ; context_index to first "number" set for offsets decoding (257)
+    call    decode_number
+    dec     de                  ; offset = upkr_decode_length(257) - 1;
+    ld      a,d
+    or      e
+    ret     z                   ; if(offset == 0) break
+    ld      (.offset),de
+.keep_offset:
+        ;             int length = upkr_decode_length(257 + 64);
+        ;             while(length--) {
+        ;                 *write_ptr = write_ptr[-offset];
+        ;                 ++write_ptr;
+        ;             }
+        ;             prev_was_match = 1;
+    ld      c,low(257 + NUMBER_BITS)    ; context_index to second "number" set for lengths decoding
+    call    decode_number       ; length = upkr_decode_length(257 + 64);
+    push    de
+    exx
+    ld      h,d                 ; DE = write_ptr
+    ld      l,e
+.offset+*:  ld      bc,0
+    IFNDEF BACKWARDS_UNPACK
+    sbc     hl,bc               ; CF=0 from decode_number ; HL = write_ptr - offset
+    ELSE
+    add     hl,bc               ; HL = write_ptr + offset
+    ENDIF
+    pop     bc                  ; BC = length
+    IFNDEF BACKWARDS_UNPACK : ldir : ELSE : lddr : ENDIF
+    exx
+    ld      d,b                 ; prev_was_match = true
+    djnz    .decompress_data    ; adjust context_index back to 0..255 range, go to main loop
+
+/*
+int upkr_decode_bit(int context_index) {
+    while(upkr_state < 32768) {
+        if(upkr_bits_left == 0) {
+            upkr_current_byte = *upkr_data_ptr++;
+            upkr_bits_left = 8;
+        }
+        upkr_state = (upkr_state << 1) + (upkr_current_byte >> 7);
+        upkr_current_byte <<= 1;
+        --upkr_bits_left;
+    }
+
+    int prob = upkr_probs[context_index];
+    int bit = (upkr_state & 255) >= prob ? 1 : 0;
+
+    int prob_offset = 16;
+    int state_offset = 0;
+    int state_scale = prob;
+    if(bit) {
+        state_offset = -prob;
+        state_scale = 256 - prob;
+        prob_offset = 0;
+    }
+    upkr_state = state_offset + state_scale * (upkr_state >> 8) + (upkr_state & 255);
+    upkr_probs[context_index] = prob_offset + prob - ((prob + 8) >> 4);
+
+    return bit;
+}
+*/
+decode_bit:
+  ; HL = upkr_state
+  ; IX = upkr_data_ptr
+  ; BC = probs+context_index
+  ; A' = upkr_current_byte (!!! init to 0x80 at start, not 0x00)
+  ; preserves DE
+  ; ** while (state < 32768) - initial check
+    push    de
+    bit     7,h
+    jr      nz,.state_b15_set
+    exa
+  ; ** while body
+.state_b15_zero:
+  ; HL = upkr_state
+  ; IX = upkr_data_ptr
+  ; A = upkr_current_byte (init to 0x80 at start, not 0x00)
+    add     a,a                     ; upkr_current_byte <<= 1; // and testing if(upkr_bits_left == 0)
+    jr      nz,.has_bit             ; CF=data, ZF=0 -> some bits + stop bit still available
+  ; CF=1 (by stop bit)
+    ld      a,(ix)
+    IFNDEF BACKWARDS_UNPACK : inc ix : ELSE : dec ix : ENDIF    ; upkr_current_byte = *upkr_data_ptr++;
+    adc     a,a                     ; CF=data, b0=1 as new stop bit
+.has_bit:
+    adc     hl,hl                   ; upkr_state = (upkr_state << 1) + (upkr_current_byte >> 7);
+    jp      p,.state_b15_zero       ; while (state < 32768)
+    exa
+  ; ** set "bit"
+.state_b15_set:
+    ld      a,(bc)                  ; A = upkr_probs[context_index]
+    dec     a                       ; prob is in ~7..249 range, never zero, safe to -1
+    cp      l                       ; CF = bit = prob-1 < (upkr_state & 255) <=> prob <= (upkr_state & 255)
+    inc     a
+  ; ** adjust state
+    push    bc
+    ld      c,l                     ; C = (upkr_state & 255); (preserving the value)
+    push    af
+    jr      nc,.bit_is_0
+    neg                             ; A = -prob == (256-prob), CF=1 preserved
+.bit_is_0:
+    ld      d,0
+    ld      e,a                     ; DE = state_scale ; prob || (256-prob)
+    ld      l,d                     ; H:L = (upkr_state>>8) : 0
+
+  IFNDEF UPKR_UNPACK_SPEED
+
+    ;; looped MUL for minimum unpack size
+    ld      b,8                     ; counter
+.mulLoop:
+    add     hl,hl
+    jr      nc,.mul0
+    add     hl,de
+.mul0:
+    djnz    .mulLoop                ; until HL = state_scale * (upkr_state>>8), also BC becomes (upkr_state & 255)
+
+  ELSE
+
+    ;;; unrolled MUL for better performance, +25 bytes unpack size
+    ld      b,d
+    DUP     8
+        add     hl,hl
+        jr      nc,0_f
+        add     hl,de
+0:
+    EDUP
+
+  ENDIF
+
+    add     hl,bc                   ; HL = state_scale * (upkr_state >> 8) + (upkr_state & 255)
+    pop     af                      ; restore prob and CF=bit
+    jr      nc,.bit_is_0_2
+    dec     d                       ; DE = -prob (also D = bit ? $FF : $00)
+    add     hl,de                   ; HL += -prob
+    ; ^ this always preserves CF=1, because (state>>8) >= 128, state_scale: 7..250, prob: 7..250,
+    ; so 7*128 > 250 and thus edge case `ADD hl=(7*128+0),de=(-250)` => CF=1
+.bit_is_0_2:
+ ; *** adjust probs[context_index]
+    ld      e,a                     ; preserve prob
+    rra                             ; + (bit<<4) ; part of -prob_offset, needs another -16
+    and     $FC                     ; clear/keep correct bits to get desired (prob>>4) + extras, CF=0
+    rra
+    rra
+    rra                             ; A = (bit<<4) + (prob>>4), CF=(prob & 8)
+    adc     a,-16                   ; A = (bit<<4) - 16 + ((prob + 8)>>4) ; -prob_offset = (bit<<4) - 16
+    sub     e                       ; A = (bit<<4) - 16 + ((prob + 8)>>4) - prob ; = ((prob + 8)>>4) - prob_offset - prob
+    neg                             ; A = prob_offset + prob - ((prob + 8)>>4)
+    pop     bc
+    ld      (bc),a                  ; probs[context_index] = prob_offset + prob - ((prob + 8) >> 4);
+    add     a,d                     ; restore CF = bit (D = bit ? $FF : $00 && A > 0)
+    pop     de
+    ret
+
+/*
+int upkr_decode_length(int context_index) {
+    int length = 0;
+    int bit_pos = 0;
+    while(upkr_decode_bit(context_index)) {
+        length |= upkr_decode_bit(context_index + 1) << bit_pos++;
+        context_index += 2;
+    }
+    return length | (1 << bit_pos);
+}
+*/
+decode_number:
+  ; HL = upkr_state
+  ; IX = upkr_data_ptr
+  ; BC = probs+context_index
+  ; A' = upkr_current_byte (!!! init to 0x80 at start, not 0x00)
+  ; return length in DE, CF=0
+    ld      de,$7FFF            ; length = 0 with positional-stop-bit
+    jr      .loop_entry
+.loop:
+    inc     c                   ; context_index + 1
+    call    decode_bit
+    rr      d
+    rr      e                   ; DE = length = (length >> 1) | (bit << 15);
+    inc     c                   ; context_index += 2
+.loop_entry:
+    call    decode_bit
+    jr      c,.loop
+.fix_bit_pos:
+    ccf                         ; NC will become this final `| (1 << bit_pos)` bit
+    rr      d
+    rr      e
+    jr      c,.fix_bit_pos      ; until stop bit is reached (all bits did land to correct position)
+    ret                         ; return with CF=0 (important for unpack routine)
+
+    DISPLAY "upkr.unpack total size: ",/D,$-unpack
+
+    ; reserve space for probs array without emitting any machine code (using only EQU)
+
+    IFDEF UPKR_PROBS_ORIGIN     ; if specific address is defined by user, move probs array there
+probs:      EQU ((UPKR_PROBS_ORIGIN) + 255) & -$100     ; probs array aligned to 256
+    ELSE
+probs:      EQU ($ + 255) & -$100                       ; probs array aligned to 256
+    ENDIF
+.real_c:    EQU 1 + 255 + 1 + 2*NUMBER_BITS             ; real size of probs array
+.c:         EQU (.real_c + 1) & -2                      ; padding to even size (required by init code)
+.e:         EQU probs + .c
+
+    DISPLAY "upkr.unpack probs array placed at: ",/A,probs,",\tsize: ",/A,probs.c
+
+    ENDMODULE
+    OPT pop